1. Field of the Invention
The present invention relates to a wafer processing method capable of handling a wafer without any damage such as a crack or the like to a device area whose rear surface is ground thinly.
2. Description of the Related Art
In the semiconductor device production process, a generally disk-like semiconductor wafer is sectioned into a plurality of areas along predetermined dividing lines called streets arranged in a lattice pattern on the front surface thereof. Devices such as ICs, LSIs or the like are formed on the areas thus sectioned. The semiconductor wafer is cut along the streets by a cutting device to be divided into individual semiconductor devices (chips). The wafer to be divided is formed at a predetermined thickness by grinding its rear surface before being cut along the streets. In recent years, a wafer has been required to be reduced in thickness to e.g. approximately 50 μm in order to achieve the weight saving and downsizing of electric devices.
It is difficult to handle the wafer ground thinly as described above. The wafer is likely to be broken during conveyance or the like. To eliminate such a problem, Japanese Patent Laid-Open No. 2007-19461 proposes a grinding method as below. A wafer is ground to form a circular recessed portion on its rear surface at a portion corresponding to a device area to leave a ring-like reinforcing portion on the rear surface at a portion corresponding to an outer circumferential redundant area surrounding the device area. However, when the wafer is divided into the individual devices, it is necessary to remove the ring-like reinforcing portion. In the past, a cutting blade has been positioned at a boundary portion between the ring-like reinforcing portion and the device area and the ring-like reinforcing portion has been removed by circularly cutting the boundary portion.